PENGARUH SHOT PEENING TERHADAP SIFAT MEKANIS DAN LAJU PERAMBATAN RETAK FATIK SAMBUNGAN FRICTION STIR WELDING PADA ALUMINIUM SERI 5083

Wartono, Prof. Ir. Mochammad Noer Ilman, S.T., M.Sc., Ph.D. IPM., ASEAN Eng

2012 | Tesis | S2 Teknik Mesin

Penelitian ini bertujuan untuk mengetahui pengaruh shot peening terhadap sifat mekanis dan laju perambatan retak fatik pada paduan Al 5083 yang telah mengalami proses friction stir welding (FSW). Pada umumnya, daerah sambungan las FSW mengalami proses pelunakan dan penurunan sifat mekanis dibanding logam induknya. Perlakuan shot peening diharapkan dapat meningkatkan sifat mekanis dan menurunkan laju perambatan retak fatik. Proses FSW dilakukan pada aluminium dengan tebal 3 mm, dengan sambungan las jenis butt joint. Mesin yang digunakan dalam proses FSW ini adalah mesin milling dengan putaran spindel sebesar 910 rpm dan kecepatan meja sebesar 18,2 mm/menit. Permukaan bahan yang telah di FSW, kemudian di-shot peening dengan menembakkan bola baja selama 6 menit, 10 menit, dan 14 menit. Hasil proses FSW tanpa shot peening (NP) dan FSW dengan shot peening (SP) kemudian diuji terhadap kekerasan, tarik statis, struktur mikro dan perambatan retak fatik. Hasil uji menunjukkan bahwa proses FSW tanpa shot peening menurunkan kekuatan tarik dan kekerasan. Proses FSW dengan shot peening (SP) dengan lamanya waktu penembakan yang bervariasi dari 6 menit (SP6), 10 menit (SP10), dan 14 menit (SP14) menunjukkan peningkatan kekuatan tarik sebesar 2,06%, 3,81%, dan 6,04%. Proses FSW dengan shot peening nilai kekerasannya semakin meningkat, peningkatan kekerasan arah transversal sebesar 13,91%, 14,37%, dan 18,89%. Peningkatan kekerasan searah tebal benda sebesar 1,09%, 6,51%, dan 7,11%. FSW yang telah di-shot peening, akan mengalami penurunan laju perambatan retak fatik yang ditandai dengan peningkatan nilai konstanta Paris (n). Peningkatan nilai konstanta Paris (n) pada FSW dengan SP6, SP10, dan SP14 masing-masing sebesar 0,241%, 5,428%, dan 13,371%

The objective of this research is to find out the effect of shot peening on mechanical properties and the rate of fatigue crack propagation in Al 5083 alloy that has undergone a process of friction stir welding (FSW). In general, local FSW welded joints undergo softening and decreased mechanical properties than the parent metal. Shot peening treatment is expected to improve the mechanical properties and reduce the rate of fatigue crack propagation. FSW process performed on aluminum with a thickness of 3 mm, with the weld type butt joint. Machines used in the FSW process is a milling machine with a spindle rotation speed of 910 rpm and a table by 18.2 mm / min. The surface of the material that has been in FSW, then in-shot peening with steel balls fired for 6 minutes, 10 minutes, and 14 minutes. The results of the FSW without shot peening (NP) and FSW by shot peening (SP) were further tested for hardness, tensile static, microstructure and fatigue crack propagation. The test results showed that the FSW process without shot peening lower tensile strength and hardness. FSW process with shot peening (SP) with a varying length of time shooting than 6 minutes (SP6), 10 minutes (SP10), and 14 minutes (SP14) showed an increase in tensile strength of 2.06%, 3.81%, and 6 , 04%. FSW process with shot peening hardness value increases, increased violence transverse directions by 13.91%, 14.37%, and 18.89%. Increased violence in the direction of the thick body of 1.09%, 6.51%, and 7.11%. FSW who had been shot peening, will decrease the rate of fatigue crack propagation is characterized by a constant increase in the value of Paris (n). Increased Paris constants (n) in FSW with SP6, SP10, and SP14 respectively 0.241%, 5.428% and 13.371%.

Kata Kunci : shot peening, sifat mekanis, perambatan retak fatik, friction stir welding